Unit Circuits Design For Long Wavelength Infrared Detector Using SOI Diode

Infrared Focal Plane(IRFPA)is widely used in military,medical treatment,industry,etc.Uncooled IRFPA has low cost and less volume due to the advantage of non-refrigeration.Composed of detector and readout circuit(ROIC),the character of IRFPA quite depends on the two elements.Silicon-on-insulator(SOI)diode detector is constructed with PN junction diodes fabricated in the SOI film and based on standard CMOS process,which can be integrated with ROIC and has become the development direction of uncooled IRFPA.The detector uses its forward voltage dependence of temperature caused by infrared radiation to achieve detection.Therefore,it is important to design a specific ROIC.In this paper,a unit circuit for long wavelength infrared detector using SOI diode has been designed.The unit circuit is a Gm-C-OP integrated amplifier,which consists of an OTA and a CTIA.The OTA converts the input voltage from the detector,into current,which is then converted to voltage by CTIA.By adopting differential input structure,the Gm-C-OP integrated amplifier can eliminate the effect of ambient temperature and improve the uniformity of the output signal.Three kinds of highly linear Gm-C-OP integrated amplifier are designed and their working principles are provided.The circuits were fabricated in a 0.35μm CMOS process under 5V supply voltage.Testing results show that the three Gm-C-OP integrated amplifiers can invert the small input voltage ranging from 0 to 2mV into a proper voltage linearly.The linearity is 97% and the dynamic range is over 2V.However,we also find a random offset voltage at the input of all the three Gm-C-OP integrated amplifiers.The last part of the paper discusses the causes,and then proposes a low offset integrated amplifier using chopper stabilization technology and shows the simulation results.